1. Technical Field
Embodiments of the present invention relate to a semiconductor device and a method of manufacturing the same and, more particularly, to a semiconductor device including a buried gate and a storage node contact and a method of manufacturing the same.
2. Related Art
Recently, although demand for large capacity of semiconductor memory devices, particularly dynamic random access memories (DRAMs), has increased, increases in capacity of DRAMs will likely reach the limit in the near future as the DRAM technology goes down below 30 nm due to the difficulty of making functioning DRAM cells with the feature size that is significantly less than 30 nm. Thus, much research effort has been made in trying to reduce the memory cell size in order to fit more memory cells in the same area. One area of this effort has been to coming up with more efficient cell layout, e.g., changing the layout from a conventional 8F2 into 6F2, where “F” refers to the feature size. The feature size typically denotes the smallest pattern size used to fabricate a given semiconductor chip.
Another method used to squeeze a greater number of the memory cells into the same chip area and obtain increased storage capacity was employing a recess gate structure that has a gate formed in a recess of a substrate. A channel region is formed along a curved recess surface, instead of a conventional planar gate structure, which has a horizontal channel region.
A buried gate structure is yet another method used to scale down the DRAM memory cell, where the gate is buried in a recess in the substrate. The whole gate is formed below the surface of in a semiconductor substrate to obtain a channel that has a longer length and a wider width in order to reduce parasitic capacitance, e.g., between a gate (a word line) and a bit line.
One challenge of implementing the buried gate structure technology is the relatively small contact area between a storage node contact and an active region. This small contact area results in relatively high contact resistance.